1. Field of the Invention
The present invention relates in general to a tamper-evident container closure and a container neck structure. More particularly, the present invention relates to a closure which is applied with an axial downward force onto the neck without relative rotation of the closure and container. After the tamper-evident feature of the invention is removed, the cap may be screwed onto and off the container as a reclosure cap.
2. Description of the Related Art
The snap-on, screw-off structures available in the prior art are of two general types-those having thread engagement as initially applied, and those without initial thread engagement. The no-thread initial engagement system has the major advantages of being simple to manufacture and apply, and achieving good re-seal on re, closure through the thread torque. However, using a liner closure with this system is somewhat difficult and the consumer may be confused by the requirement of twisting the closure relative to the neck after the container is initially opened by a lifting motion. Examples of closure systems having no-thread initial engagement are those taught by U.S. Pat. No. 4,561,553 to Crisci, and U.S. Pat. No. 4,946,055 to Towns et al.
Systems having partial to full thread engagement after the initial application have several advantages over the no-thread system, including the elimination of consumer confusion. However, the initial thread engagement systems often do not offer the manufacturing and application advantages available with the no-thread system. With some systems, the closure must be twisted relative to the container at some point during the application process. An example of such a closure is shown in U.S. Pat. No. 4,625,875 to Carr. Other concepts, such as that taught by Miskin in the European Patent Specification No. 0 118 267 do not require orientation or twisting during application, and accommodate for the inevitable closure height variation after application by employing an extended plug to seal against the inside bore of the container neck.
Both the system taught by Carr and Miskin suffer from the requirement that the tamper evident band must be expanded over a restrictive container bead during the application process. This requirement leads to application difficulties, especially in the Miskin concept where the rotary assist as taught by Carr is not employed. An additional problem common to both the Carr and Miskin concepts is that the lower tamper evident band is joined to the upper closure skirt through bridges requiring mold slides for formation, a feature which greatly increases the cost and complexity of injection molding tooling. Finally, in both the Miskin and Carr concepts the tamper evident band remains on the bottle after initial opening, a feature which thwarts effective container recycling.
Other systems available in the art include screw-on, screw-off structures which also offer the advantages of initial thread engagement and elimination of consumer confusion. An example of this type of closure is shown in U.S. Pat. No. 3,980,195 to Fillmore. The system taught by Fillmore includes a threaded, tamper-evident closure with a removable band. The interior of the removable band is formed with a one-way ratchet, which cooperates with projections formed on the neck to prevent unscrewing of the container. When the closure is initially twisted onto the neck, the ratchet teeth slip over the projections on the neck. The band must be removed prior to opening the container.
The snap-on, screw-off structures have several advantages not found with the closure taught by Fillmore. The application process used with the screw-on, screw-off systems is quite complex, since the cap must be turned or rotated relative to the container until the closure is fully seated. The frangible connections between the tamper-evident band and the closure must be sufficiently strong to prevent partial separation when the cap is twisted onto the container, increasing the costs of manufacture. The consumer will also often have difficulty removing the closure, since the band must first be separated from the rest of the cap.
This invention provides a snap-on, screw off system with partial or full thread initial engagement by reason of a unique thread design, a unique tamper-evident band and optional means for orienting the closure and container threads to achieve registration prior to straight axial application. The present invention offers considerable advantages over prior structures as is evident from the description of the related art and the following description of the invention.